RECOVERY OF METAL VALUES FROM SM-CO MAGNETS SCRAP

A possibility to develops a wet method, consisting of leaching, solvent extraction and precipitation, to recover metal values from scrap Sm-Co magnets including SmCo5 and Sm2Co17 was investigated. All component metals are readily leached out in 2 kmol . m(-3) HNO3 solution. By contrast, HCl and H2SO4 are less effective leachants, leaving Cu in the leach residue. Firstly Fe(III) and Zr(IV) were extracted in an organic phase with D2EHPA from the leach solution, then Sm(III) was extracted with the same extractant after pH adjustment. Precipitation stripping of Sm(III) with oxalic acid was found to be effective in avoiding the co-precipitation of other metals. Cu(II) and Co(II) in the raffinate can be extracted with LIX65N and D2EHPA, respectively, and stripped with an aqueous H2SO4 solution. Fe(III) and Zr(IV)-loaded D2EHPA organics can be stripped with oxalic acid, followed by the photo-chemical reduction of Fe(III)-oxalate to the Fe(II) state to selectively precipitate, leaving Zr(IV) oxalate in the stripped solution. Based on these findings, a novel process was proposed with the values of expectant material balance.